1. Field of the Invention
Embodiments of the present invention generally relate to a magnetic read head for use in a hard disk drive (HDD).
2. Description of the Related Art
The heart of a computer is a magnetic disk drive which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider towards contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air a slight distance from the surface of the rotating disk. When the slider rides on the air, the write and read heads are employed for writing magnetic impressions to, and reading magnetic signal fields from, the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
In a read head, a giant magnetoresistive (GMR) sensor, or a tunnel junction magnetoresistive (TMR) sensor has been utilized for sensing magnetic fields from the rotating disk. A typical GMR sensor includes a non-magnetic layer barrier such as MgO or spacer such as AgSn sandwiched between a pinned layer and a free layer, while a typical TMR sensor includes a thin non-magnetic, electrically insulating barrier layer sandwiched between a pinned layer and a free layer. Magnetic shields are positioned above and below the sensor stack and can also serve as first and second electrical leads so that the electrical current travels perpendicularly to the plane of the free layer, spacer layer and pinned layer. This configuration is known as the current perpendicular to the plane (CPP) mode of operation. The magnetization of the pinned layer is pinned perpendicular to the ABS and the magnetic moment of the free layer is located parallel to the ABS, but free to rotate in response to external magnetic fields. The magnetization of the pinned layer is typically pinned by exchange coupling with an antiferromagnetic layer such as IrMn.
The scaling of read head dimensions to achieve higher areal density has pushed the pinned layer stripe height so short that the edge degradation and thermal stability of the pinned layer start to cause magnetic head performance and reliability issues. One approach to improve the read head stability is to extend the pinned layer from the backedge of the free layer stripe height. This approach is known as the shape enhanced pinned layer (SEP). The method of forming the SEP structure is important to reduce potential instability issues. Thus there is a need for an improved method of forming a SEP structure and an improved SEP structure design.